1. Field of the Invention
The present invention relates to an improved electrical switch and a linkage therefor. More particularly, the present invention relates to a high voltage switch of the vertical break type and to a linkage therefor.
2. Description of the Prior Art
High voltage switches having a pivotable switch blade and a stationary contact selectively engageable by the blade are often categorized as either disconnect switches or interrupter switches. A disconnect switch is one designed to isolate a line or to open a circuit where neither the line nor the circuit are energized at the time of switch operation. An interrupter switch may take the same form as a disconnect switch, but has the additional provision of a device called an interrupting unit, which permits operation of the switch while the line or circuit is energized. The interrupting unit provides a parallel path for electric current which is selectively directed thereto during switch blade movement. Thus, no external arcing occurs between the switch blade and the stationary contact when they are disengaged. Rather, the arc is permitted to form internally within the interrupting unit where it is interrupted or extinguished. See commonly-assigned U.S. Pat. No. 3,909,570 issued to Harner et al. for a description of one type of interrupting unit, and also commonly-assigned U.S. Patent application Ser. No. 775,904 filed on the same date herewith, for an interrupting unit designed for use at voltages of up to 34.5 kV.
It is well known in the art that various metallic parts of high voltage switches of either category must be maintained predetermined distances apart both in their open and closed positions. This separation is necessitated by the presence of high voltage and prevents undesired arcing between the separated parts. It is generally accepted that vertical-break or vertical-opening switches permit minimum spacing between the poles of polyphase high voltage switches while achieving the necessary separation.
Generally speaking, a vertical-break switch is one where the switch blade is hinged to a first insulator to move into and out of engagement with the stationary contact mounted on a seconc insulator. Movement of the blade is included in a plane which also includes the insulators. In the most desirable form of vertical-break switch, such blade movement is effected by an insulative push rod connected between the blade and an operating mechanism thus permitting the minimum number of insulators per pole. However, until the present invention, such vertical-break switches have been confined to use in indoor, or metal-enclosed switchgear, primarily because maximum switch blade movement away from the stationary contact has been limited to about 70.degree.. This limitation is established by interference between the push rod and other portions of the switch where more than 70.degree. opening has been attempted. Thus, the use of vertical-break switches operated by a push rod in outdoor environments has been virtually non-existent. This is because, among other reasons, outdoor switches require at least 90.degree. opening so that a human operator may visually determine, by observing the presence of a 90.degree. air gap between the blade and the stationary contact, that the switch is indeed open.
Outdoor switches of the so-called side-break variety are also well-known. They are usable at high voltages, such as 34.5 kV, but require more room overall than vertical-break switches, because adequate spacing must be maintained between the parts of the rspective switch poles both in the switch-open and switch-closed positions. Moreover, side-break switches, although having only two insulators, generally move the switch blade away from their stationary contacts by rotation of an insulator connected thereto through the required angle. This construction requires a mechanically strong rotating insulator bearing assembly.
Vertical-break switches providing 90.degree. are also known, but these usually include complicated conversion of rotary motion to pivotal blade motion, as well as a third insulator to support the motion-converting, blade-moving mechanism.
At times a triangular configuration for a switch is preferred because of the triangular configuration of the conductors connected to the switch. The art has not had a simple, economical vertical-break switch for such conductor configurations at high voltages. Rotary, side-break types of triangular switches are known, but they suffer from the same shortcomings as do all side-break switches. Similarly, 90.degree. opening, triangular switches of the three insulator variety, with the shortcomings thereof, are known.
Accordingly, one object of the present invention is to provide an improved electrical switch and linkage therefor which obviate the shortcomings of the prior art, above-described.
Another object of this invention is the provision of a high voltage switch of the vertical-break type and of a linkage therefor which makes such a switch compact, practical and simple, requiring a minimum number of insulators.
Yet another object of the present invention is the provision of a vertical-break type of switch, usable with or without an interrupting unit, and usable at high voltages such as 34.5 kV, wherein the blade of the switch is pivoted by a push rod, which switch includes a novel linkage permitting the attainment of this objective.
A still further object of the present invention is to provide a vertical-break switch, as described immediately above, wherein the switch blade moves to its open position from its closed position through an angle of at least 90.degree., and wherein the push rod and a drive mechanism therefor form an over-center toggle in the open position, both of these objectives being attained through the use in the switch of the novel linkage of the present invention. These objectives being attained, inadvertent closing of the switch due to wind or the like is prevented.
Yet another object of the present invention is the provision of a vertical-break switch and novel linkage as described immediately above, wherein, during operation of the switch, dielectric clearances of the various parts of the switch are not adversely affected.